Laser cutting/engraving machines for cutting and engraving work pieces have been enjoying increased sales as the machines increase in performance and decrease in cost, thus making them available for a wider variety of cutting and engraving applications. Typically, laser cutting/engraving machines operate by directing a laser beam along x and y axes relative to a fixed work surface bearing a work piece. For many applications, the surface to be cut or engraved is substantially planar and the work piece can simply be set upon the work surface and secured thereto while the laser beam is directed along the x and y axis by, for example, a programmable microprocessor. However, where a surface to be engraved is curved, for example cylindrical, it can not be readily engraved in the same manner as a planar surface because the curved surface varies in distance along a z axis from the laser beam source. To address this problem, numerous manufacturers of laser cutting/engraving machines have developed rotary fixtures to rotate work pieces having cylindrical and other curvilinear surfaces (which will be collectively called “substantially cylindrical” herein) about an axis of rotation of the work piece to present the engraving surface at a fixed distance along the z axis from the laser source.
Typically laser cutting/engraving rotary fixtures include a master spindle operatively associated with a motor for rotating the master spindle and a slave spindle spaced from the master spindle along an axis of rotation. A chuck is provided in operative association with each spindle for securing a substantially cylindrical work piece between the master and slave spindles along an axis of rotation of the work piece. The slave spindle is typically movable relative to the master spindle along the axis of rotation so that a work piece can be compressed between the chucks associated with the spindles to secure the work piece for rotation about the axis of rotation by actuation of the master spindle. Known laser cutting/engraving rotary fixtures provide chucks presenting either an effectively concave contact surface for engaging an outer diameter of a substantially cylindrical work piece or an effectively convex contact surface for engaging an inner diameter of a substantially cylindrical work piece. As used herein, “effective concave” and “effectively convex” means a surface or surface segments that function as curved or linear concave or convex surfaces. If a substantially cylindrical work piece having two outer diameters and no inner diameter is provided, two opposing effectively concave chucks must be used on the master and slave spindles. If the work piece presents only two inner diameters suitable for engagement, a convex chuck must be associated with each of the master and slave spindles. Thus, conventional laser cutting/engraving rotary fixtures require up to four chucks (two with effectively concave contacting surfaces and two with effectively convex contacting surfaces). In addition, known laser cutting/engraving rotary fixtures require removal of an effectively concave or convex chuck in order to replace it with the other. Typically, removal of the chucks requires use of tools. Thus, between keeping track of the necessary effectively concave and convex chucks and the tools for changing out the chucks, conventional systems can create a cluttered work space and the opportunity for losing essential items. In addition, the process of changing out the effectively concave or convex chucks can be time consuming and difficult, particularly when a variety of different substantially cylindrical objects are being engraved. Yet another problem with existing laser cutting/engraving rotary fixture chucks is manufacturers must carry at least two SKU's to provide their customers with the necessary chuck options.
The present invention is intended to overcome one or more of the problems discussed above.